Use hashmap instead of linked list

[ligurio]

unreliablefs uses linked list for error injections, see

unreliablefs/unreliablefs_errinj.c

Lines 183 to 235 in c6a6b1e

	/* apply error injections defined in configuration one by one */
	TAILQ_FOREACH(err, conf.errors, entries) {
	unsigned int p = rand_range(MIN_PROBABLITY, MAX_PROBABLITY);
	if (!(p <= err->probability)) {
	fprintf(stderr, "errinj '%s' skipped: probability (%d) is not matched\n",
	errinj_name[err->type], err->probability);
	continue;
	}
	const char* op_name = fuse_op_name[operation];
	if (is_regex_matched(err->path_regexp, path) != 0) {
	fprintf(stderr, "errinj '%s' skipped: path_regexp (%s) is not matched\n",
	errinj_name[err->type], err->path_regexp);
	continue;
	}
	if (is_regex_matched(err->op_regexp, op_name) != 0) {
	fprintf(stderr, "errinj '%s' skipped: op_regexp (%s) is not matched\n",
	errinj_name[err->type], err->op_regexp);
	continue;
	}
	fprintf(stdout, "%s triggered on operation '%s', %s\n",
	errinj_name[err->type], op_name, path);
	switch (err->type) {
	case ERRINJ_NOOP:
	rc = -ERRNO_NOOP;
	break;
	case ERRINJ_KILL_CALLER: ;
	struct fuse_context *cxt = fuse_get_context();
	if (cxt) {
	int ret = kill(cxt->pid, DEFAULT_SIGNAL_NAME);
	if (ret == -1) {
	perror("kill");
	}
	fprintf(stdout, "send signal %s to TID %d\n",
	strsignal(DEFAULT_SIGNAL_NAME), cxt->pid);
	}
	break;
	case ERRINJ_ERRNO:
	rc = op_random_errno(operation);
	fprintf(stdout, "errno '%s'\n", strerror(rc));
	rc = -rc;
	break;
	case ERRINJ_SLOWDOWN: ;
	struct timespec ts = {};
	ts.tv_nsec = err->duration;
	fprintf(stdout, "start of '%s' slowdown for '%d' ns\n", op_name, err->duration);
	if (nanosleep(&ts, NULL) != 0) {
	perror("nanosleep");
	} else {
	fprintf(stdout, "end of '%s' slowdown with '%d' ns\n", op_name, err->duration);
	}
	break;
	}
	}

On each operation, it traverses a list with error injections, and it is not optimal from performance point of view, algorithmic complexity is O(N). It is better to use hashmap. For example, a static hashmap implemented by gperf¹.

Footnotes

1. https://www.gnu.org/software/gperf/manual/gperf.html ↩